1. Technical Field
The present invention relates to a pressurizing-type pen in which the ink contained in an ink refill is pressurized by the user at the time of writing to assist in writing.
2. Related Art
Pressurizing-type pens such as ball point pens have been known in which, when the front end of a refill accommodated in a pen barrel is protruded to a writing position by a knocking operation, the ink supplied to the writing tip at the front end of the refill can be pressurized by applying air pressure to a rear space of the refill filled with the ink. For example, JP-A-2005-246648 and JP-A-2005-138356 describe such pressurizing-type pens.
In pressurizing-type pens, generally, when the front end of a refill is fed from a barrel by a knocking operation, the periphery of a rear portion of the refill is closed to form a closed space and air in the closed space is compressed to pressurize the rear space of the refill. In many cases, as a sealing member for forming the closed space, an elastic member which is in sliding contact with the periphery of the refill is used. For example, the pressurizing-type pen described in JP-A-2005-246648 uses an O-ring having such an inner diameter that makes it possible to slidably move in sealing contact with the periphery of an outer face of an ink reservoir. In the ball point pen described in JP-A-2005-138356, an annular elastic member formed by an O-ring is constituted such that the elastic member sealingly and slidingly contacts with and detachs from the inner face of a cylinder.
Accordingly, in conventional pressurizing-type pens, when the refill moves in an axial direction, the sealing member is rubbed against the outer periphery face of the refill or against the inner face of the cylinder, and therefore the sealing member is apt to abrade. Further, since the O-ring itself is required to expand or shrink, the O-ring is likely damaged and it sometimes becomes impossible to retain an adequate sealing condition. In addition, since the air compressed by the pressurizing mechanism does not always properly act on the ink, the pressurization of the ink sometimes becomes uncertain. Further, in some cases, the pressurizing mechanism is retracted in such a condition that sealing is maintained without sufficient pressure reduction, and the ink is sucked out of the refill by suction.
Further, in conventional pressurizing-type pens, many pens employ a so-called rotating cam-type feeding mechanism as a mechanism for feeding a refill by a knocking operation, but such pens have the above pressurizing mechanism incorporated therein, and therefore the entire mechanism becomes complicated making it difficult to feed the refill securely.